1. Field of the Invention
This invention relates generally to media reservation in an IP network.
2. Description of Related Art
Modern Internet Protocol (IP) networks enable users to communicate in more ways than ever before. Users may now exchange information using Voice over IP (VoIP), video calls, video conferencing, streaming multimedia, instant messaging, and countless other applications. As the number of methods of communication has increased, the signaling required to establish and maintain connections has become more complex.
The Session Initiation Protocol (SIP), defined in RFC 3261, is a signaling protocol developed to set-up, modify, and terminate multimedia sessions between users in an IP network. By providing a standard format for setup messages, SIP enables devices to negotiate parameters of a multimedia session in a seamless manner, regardless of the underlying transport protocols. Given its simplicity and flexibility, many current systems utilize SIP messaging and many systems in development will also use SIP.
Briefly stated, SIP enables an initiating user, or user agent client (UAC), to request that a connection be established with, another user, known as the user agent server (UAS). The UAC sends a connection request to a proxy server, which coordinates the exchange of setup messages between the UAC and UAS and provides each party with information necessary to establish the connection. After the connection is initiated, the UAC and UAS may directly exchange messages using an appropriate transport protocol, such as the Real-Time Transport Protocol (RTP).
Although RFC 3261 greatly simplifies the process of establishing a connection between two users, the standard does not provide an effective means for modifying Quality of Service (QoS) and guarding against: denial of service attacks. RFC 3313, published shortly after RFC 3261, attempts to solve these problems by defining an extension to integrate QoS admission control into SIP signaling messages, in particular, RFC 3313 seeks to improve users' Quality of Experience (QoE) by allowing specific media reservation in Layers 1-3 of the Open Systems Interconnection (OSI) model.
In a system supporting the RFC 3313 extension, when a UAC sends a connection request through a proxy, the proxy authenticates the caller and verifies that the caller is authorized to receive QoS. The proxy then exchanges messages with an edge router or a policy decision point (PDP) to obtain an authorization token and forwards this token to the UAC. Upon initiation of the connection, the UAC sends the token to the edge router, which provides QoS accordingly.
As should be apparent from the above description, the process defined in RFC 3313 requires a significant amount of additional messaging to establish QoS for a SIP connection. In particular, the link between the proxy and the edge router experiences a significant amount of additional traffic. Furthermore, hardware and/or software on each device involved in the message exchange must be modified to ensure that the devices properly handle the RFC 3313 extension.
Accordingly, there is a need for a system and method that allow for a simplified mechanism of providing QoS in a connection initiated using SIP signaling messages. In particular, there is a need for a solution that minimizes the use of additional messages and eliminates the need to implement additional functionality on every device in the system.
The problems described above are illustrative of those that are addressed by the various exemplary embodiments and are not intended to be exhaustive or limiting of the possible problems addressed or solved. Thus, other problems solved by the various exemplary embodiments will be apparent to those of ordinary skill in the art.